SFU biologist discovers dangerous mosquito close to home

This particular species can transmit diseases like West Nile virus. - Image by Zach Chan

Getting a mosquito bite in the Metro Vancouver area just got more risky. Aedes japonicus, an invasive mosquito that can transmit several viral diseases, has been found for the first time in Western Canada, in Maple Ridge.

Peter Belton, a retired biologist at SFU, was one of the researchers who identified the Aedes japonicus mosquitos in BC’s Lower Mainland. They were found breeding in water in a backyard.

The species can transmit West Nile virus, three types of encephalitis, and Chikungunya, a disease prevalent in Asia that recently made appearances in the Caribbean and the southern United States.

This particular mosquito is an invasive species, originating in Asia but having spread around the world. In 2001, this species was found in King County Washington, and in 2008 specimens were collected in southern Washington and Oregon. The larvae are often found developing in rainwater in used car tires sitting stagnant for an extended period of time.

Belton discussed how the mosquito got introduced to these new environments: “This one arrived in the eastern US in 1998, probably as eggs in used car tires, imported from Japan or Korea for retreading. It probably got to Europe the same way in 2000.”

He continued, “It has spread to 33 adjacent eastern states and five Canadian provinces since then. We think humans are responsible for the long distances, but the mosquitoes can probably fly for shorter hops.”

The species has also been found 13 kilometers from Maple Ridge, in Mission. Researchers have since concluded that there are at least two populations in the Lower Mainland. The mosquito’s larvae were first identified in July 2014 in Maple Ridge, and since the beginning of 2015, more than 200 have been counted.

The Peak asked Belton whether the increase in the population of Aedes japonicus in North America increases the risk of disease transmission.

“Yes, obviously there is more chance of a female [mosquito] acquiring a virus from an infected (viraemic) bird or mammal. It is thought to be transmitting La Crosse virus in the southern Appalachians,” said Belton.

The mosquito could become a significant threat to both animal and human health if global warming continues to increase, as this will impact the distribution of the diseases the mosquito can carry.

“Higher temperatures increase the biting rates and activity of the mosquitoes, and also increase the development of viruses” said Belton.

Belton explained that “[W]e need to monitor with traps or by sampling containers (roadside catch basins are often used for this). If a virus appears, larvae can be controlled with specific bacteria.”

While there is no evidence so far that Aedes japonicus is transmitting disease, taking these precautions could prevent a public health risk.